robotic arms and robots

Abstract

A robotic arm and a robot are provided. The robotic arm (100, 10, 20, 30, 40, 50, 60) includes multiple joints (121-127, 200a-200d, 511-513) and multiple connecting arms (131-137, 301, 302, 411-413). The connecting arms are connected sequentially via joints. At least two joints each include a sensor (205) configured to measure force and torque information applied to more than one of the six degrees of freedom (DOF) on their respective joints.

Description

[0001] This application is a divisional application of application number 202080000958.4 (Invention title: Mechanical arm and robot, application date: April 3, 2020). Technical Field

[0002] This invention relates generally to robotics, and more particularly to robotic arms and robots. Background Technology

[0003] Robotic arms are used in many industrial sectors to assist in manufacturing, assembly, and other operations. In some applications, it is advantageous to use torque-based control techniques to control the movement of the robotic arm. Such robotic arms rely on precise torque measurement.

[0004] Conventional robotic arms have only one single-degree-of-freedom (DOF) torque sensor in each joint to measure the torque generated or applied to each corresponding joint. This configuration can introduce errors regarding the torque and other forces measured at the joints, and therefore presents many disadvantages for the operation of such conventional robotic arms. Summary of the Invention

[0005] Therefore, the present invention aims to provide a robotic arm and a robot.

[0006] The technical solution adopted by this invention is to provide a robotic arm. The robotic arm includes multiple joints and multiple connecting arms. The connecting arms are connected sequentially via the joints. At least two joints each include a sensor configured to measure force and torque information applied to more than one of the six degrees of freedom (DOF) on a corresponding joint among the at least two joints.

[0007] Another technical solution adopted by the present invention is to provide a robot. The robot includes multiple joints and connecting arms. The connecting arms are connected sequentially via the joints. Each joint includes a sensor configured to measure force and torque information applied to more than one of the six degrees of freedom (DOF) of the corresponding joint. Attached Figure Description

[0008] To more clearly explain the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly described below. The drawings in the following description are merely exemplary embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative work.

[0009] Figure 1 A structural diagram of a robotic arm according to an embodiment of the present invention is shown.

[0010] Figures 2 to 5Several exemplary arrangements of multi-degree-of-freedom force and / or torque sensors for joints according to some embodiments of the present invention are shown.

[0011] Figures 6A to 6C A schematic diagram of a robotic arm is shown, in which each joint includes a single-degree-of-freedom torque sensor.

[0012] Figures 7A to 7C A schematic diagram of a robotic arm is shown, in which each joint includes a multi-degree-of-freedom force and / or torque sensor. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the accompanying drawings and examples. As will be apparent to those skilled in the art, the embodiments described herein are merely exemplary and represent only a subset of all such embodiments. In particular, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without inventive effort fall within the scope of the present invention.

[0014] Most traditional advanced robotic arms have a single-degree-of-freedom torque sensor in each joint to measure the torque generated by each corresponding joint for joint torque control. This torque-controlled robotic arm has the following drawbacks.

[0015] First, preventing torque sensors from being affected by forces and torques applied in other directions (e.g., directions different from the torque dimension the sensor is designed to sense) is difficult; this is known as sensor crosstalk. As a result, the sensor deviates from the true torque value under different load conditions (e.g., joint torque coupling). Mechanical structures designed to reduce this effect are often available, such as using bearings to constrain the forces and torques that can be transmitted through the torque sensor. However, mechanical structures cannot always completely eliminate this effect. For example, bearings can still deform under bending moments perpendicular to the axis of rotation. Therefore, the aforementioned effect can be reduced, but not eliminated. Sensor design techniques exist to reduce torque sensor crosstalk effects, such as using multiple transducers (e.g., strain gauges) at different locations to compensate for this effect. However, the effectiveness of such techniques is limited by design complexity, compactness requirements, and manufacturing precision. Second, in conventional robots, torque sensors must be protected by a set of bearings to reduce joint torque coupling effects. Therefore, the controlled torque transmitted by the joint will be reduced by friction from the bearings, which compromises the accuracy of force control. Third, torque sensors are typically placed close to gear transmission mechanisms (e.g., harmonic drives). When actuated, these mechanisms can apply torque and force to the sensor in other directions, which also reduces sensing accuracy. One phenomenon that reduces sensing accuracy is the appearance of torque fluctuations in the sensed signal. Fourth, due to manufacturing limitations such as non-ideal part tolerances and concentricity inherent in articulated mechanisms, the sensor will experience different micro-deformations when the articulated output position varies, which also reduces sensing accuracy.

[0016] Therefore, the present invention provides a robotic arm having multi-degree-of-freedom force and / or torque sensors in at least some joints to sense more force and / or torque information transmitted through the joints and connecting arms compared to conventional robotic arms.

[0017] Figure 1 A structural diagram of a robotic arm 100 according to an embodiment of the present invention is shown. The robotic arm 100 may include a plurality of connecting arms 131-137 and a plurality of joints 121-127. The connecting arms 131-137 are connected sequentially via joints 121-127. Joints 121-127 may have two basic types: pitch joints and roll joints. Roll joints (e.g., as shown in the diagram) Figure 1 The joints 121, 123, 125, and 127 shown can provide rotation about the longitudinal axis of the adjacent connecting arm, and the pitch joints (e.g., as shown) Figure 1 Joints 122, 124, and 126 shown can provide rotation about an axis substantially perpendicular to the tilt joint axis. In some examples, end effector 140 may be attached to the last joint (e.g., joint 127). Figure 1In the illustrated embodiment, the robotic arm 100 is a 7-axis robotic arm. It should be understood that the technical solutions disclosed below can also be implemented for other types of robotic arms with more or fewer axes.

[0018] At least two of joints 121-127 may each include a sensor configured to measure force and torque information (including three-directional force and three-directional torque information) in more than one of the six degrees of freedom (DOF) of their respective joints. For example, the sensor may be a multi-DOF force and / or torque sensor. For instance, joints 126 and 127 may be equipped with multi-DOF force and / or torque sensors, or all joints 124-127 may be equipped with multi-DOF force and / or torque sensors. Alternatively, in some embodiments, all joints 121-127 may each include a multi-DOF force and / or torque sensor.

[0019] In some embodiments, the sensor may be configured to measure the torque applied to its respective joint in the actuation direction. For example, if the pitch joints 122, 124, or 126 include multi-degree-of-freedom force and / or torque sensors, the sensor may be used to measure the torque in the Y direction (perpendicular to the joint). Figure 1 The torque in the X and Z directions (as shown). If the roll joints 121, 123, 125, or 127 include a multi-degree-of-freedom force and / or torque sensor, the sensor can be used to measure the torque in the longitudinal direction between adjacent connecting arms. Furthermore, the sensor can also be configured to measure force and torque information in at least one of the other five degrees of freedom. That is, the sensor can also be configured to measure one or more of the other three directions of force and / or one or more of the other two directions of torque. For example, the multi-degree-of-freedom force and / or torque sensor in the corresponding joint can be configured to measure torque in the actuation direction and force in each of the X, Y, and Z directions.

[0020] For better robot dynamics and control performance, the stiffness of each sensing degree of freedom along the multi-degree-of-freedom force and / or torque sensors can be optimized. In one example, the structural stiffness of the multi-degree-of-freedom force and / or torque sensors in the actuation direction of the corresponding joint (e.g., around the joint axis) can be lower than the structural stiffness of the multi-degree-of-freedom force and / or torque sensors in other directions. In such an example, sensing sensitivity and resolution on the degree of freedom that can be actively adjusted by actuation can be improved. In such an example, the stiffness on other degrees of freedom of the structure can also be kept at a high level to maintain high structural stiffness of the entire robotic arm for better control performance and higher mechanical and control bandwidth.

[0021] In some embodiments, the multi-DOF force and / or torque sensor may be a six-DOF force and torque sensor, capable of sensing torque and force information across all six degrees of freedom transmitted through the corresponding joint and the adjacent connecting arm in which the joint resides. Six-DOF force and torque sensors are designed to sense all forces and torques experienced at the joint and the adjacent connecting arm, and therefore remain accurate under any combination of forces and torques. U.S. Patent Application No. 16 / 456,588 discloses an exemplary six-DOF force and torque sensor. However, other types of six-DOF force and torque sensors may also be utilized in other examples of the invention.

[0022] Figures 2 to 5 Different arrangements of sensors in the joint are shown. Figures 2 to 5 In this design, joints 200a-200d each include an input section 201, an output section 202, a motor 203, a gear transmission mechanism 204, a multi-degree-of-freedom force and / or torque sensor 205, and one or more bearings 206. The stator of the motor 203 can be fixed to the input section 201, and the rotor of the motor 203 can be fixed to the output section 202, such that the motor 203 can drive the output section 202 to rotate relative to the input section 201. The gear transmission mechanism 204 can be connected to the rotor of the motor 203 to regulate the rotational speed and output torque of the output section 202. In some embodiments, the gear transmission mechanism 204 can be a harmonic drive mechanism. In some examples, the bearings 206 can be located between the input section 201 and the output section 202 to allow relative rotation between the two sections.

[0023] In such Figure 2 In the illustrated embodiment, the multi-degree-of-freedom force and / or torque sensor 205 of joint 200a can be placed between input 201 and output 202 (e.g., between gear transmission mechanism 204 and output 202), similar to a joint with a single-degree-of-freedom torque sensor. In this embodiment, since bearing 206 is designed to withstand bending moments from output 202 to input 201, the multi-degree-of-freedom force and / or torque sensor 205 can be configured to measure only the torque in the actuation direction of joint 200a and the axial force transmitted from output 202 to input 201.

[0024] In such Figure 3In the illustrated embodiment, the multi-degree-of-freedom force and / or torque sensor 205 of joint 200b can be placed between the input section 201 of joint 200b and the preceding connecting arm 301. In this embodiment, the multi-degree-of-freedom force and / or torque sensor 205 can be designed to measure force and torque information of any number of the six degrees of freedom. For example, the multi-degree-of-freedom force and / or torque sensor 205 can be a three-degree-of-freedom force sensor capable of measuring force information in all three force directions, a three-degree-of-freedom torque sensor capable of measuring torque information in all three torque directions, a four-degree-of-freedom force and torque sensor capable of measuring force information in all three force directions and torque in the actuation direction of joint 200b, etc.

[0025] In one embodiment, the multi-DOF force and / or torque sensor 205 may be a six-DOF force and torque sensor capable of sensing all forces and torques transmitted between the preceding connecting arm 301 and the input portion 201 of the joint 200b. The joint 200b may also include a sensor circuit board 207 communicating with the multi-DOF force and / or torque sensor 205. The sensor circuit board 207 may be located at the input end of the input portion 201 of the joint 200b and adjacent to the multi-DOF force and / or torque sensor 205. This example configuration can greatly simplify the wiring configuration of the multi-DOF force and / or torque sensor 205 and the sensor circuit board 207.

[0026] In such Figure 4 In the illustrated embodiment, the multi-degree-of-freedom force and / or torque sensor 205 of joint 200c can be placed between the output portion 202 of joint 200c and the subsequent connecting arm 302. In this embodiment, the multi-degree-of-freedom force and / or torque sensor 205 can be designed to measure force and torque information of any number of the six degrees of freedom. For example, the multi-degree-of-freedom force and / or torque sensor 205 can be a three-degree-of-freedom force sensor capable of measuring force information in all three force directions, a three-degree-of-freedom torque sensor capable of measuring torque information in all three torque directions, a four-degree-of-freedom force and torque sensor capable of measuring force information in all three force directions and torque in the actuation direction of joint 200b, etc.

[0027] In one embodiment, the multi-DOF force and / or torque sensor 205 may be a six-DOF force and torque sensor capable of sensing all forces and torques transmitted between the output portion 202 of joint 200b and the subsequent connecting arm 302. In this embodiment, the multi-DOF force and / or torque sensor 205 is placed at the input end or inside the corresponding joint (as described in the above embodiments). Figure 2 or Figure 3Compared to (as shown), the less compliance between the actuation output and the sensing component (e.g., the multi-degree-of-freedom force and / or torque sensor 205) can improve the torque sensing accuracy and control performance of the joint 200c.

[0028] exist Figure 3 and Figure 4 In the illustrated embodiment, since sensor 205 is a multi-degree-of-freedom force and / or torque sensor, it can be placed outside the input section 201, output section 202, and bearing 206 without compromising sensing accuracy. Therefore, the multi-degree-of-freedom force and / or torque sensor 205 can be flexibly mounted anywhere on the joint to gain design benefits, such as simplified wiring configuration or optimized joint design for better dynamic and control performance.

[0029] exist Figure 5 In the illustrated embodiment, joint 200d may include two multi-degree-of-freedom force and / or torque sensors 205 and 207. The first sensor 205 may be located between the input portion 201 of joint 200d and the preceding connecting arm 301, while the second sensor 207 may be located between the output portion 202 of joint 200d and the following connecting arm 302. Either sensor 205 or 207 may be redundant to the other to improve the accuracy of force and torque measurements. In some examples, additional redundant sensors in the robotic arm 100 may be used for cross-checking for fault detection and improved safety. In some embodiments, sensors 205 and 207 may be substantially identical. In other embodiments, sensor 207 may differ from sensor 205. For example, the force and torque information measured by sensor 207 may differ from the force and torque information measured by sensor 205.

[0030] Figures 6A to 6C An example scenario is shown where each joint of a robotic arm includes a single-degree-of-freedom torque sensor. In this example, the robot includes three connecting arms 411-413, three joints 511-513, and an end effector 414. Each of joints 511-513 includes a sensor configured to measure torque only in the actuation direction of the corresponding joint. When a load 610 is applied to the end effector 414, the sensors in joints 511 and 513 can each sense a single degree-of-freedom torque, such as... Figure 6A As shown on robotic arm 10. When load 620 is applied to connecting arm 413, sensors in joints 511 and 512 can each sense a degree of freedom torque, such as... Figure 6B As shown on the robotic arm 20. When loads 610 and 620 are simultaneously applied to the end effector 414 and the connecting arm 413, respectively, the sensors in joints 511-513 can each sense a degree of freedom torque, such as... Figure 6CThe robotic arm 30 is shown in the example. However, in this example scenario, the robot cannot correctly identify the two loads 610 and 620. Instead, the robot may mistakenly identify loads 610 and 620 as a single force load 630 on the end effector, because the sensing results of the multi-degree-of-freedom sensor when applying a single load 630 are the same as those when applying two loads 610 and 620. Therefore, this could compromise the robot's control performance and its ability to operate normally in complex environments.

[0031] In comparison, Figures 7A to 7C An example scenario is shown where each joint of a robotic arm includes multi-degree-of-freedom force and / or torque sensors. In this example, the robot includes three connecting arms 411-413, three joints 511-513, and an end effector 414. Each of the joints 511-513 includes a sensor configured to measure force and / or torque information for multiple degrees of freedom, such as torque in the actuation direction of the corresponding joint and two forces perpendicular to the actuation direction of the corresponding joint. When load 610 is applied... Figure 7A When the load 620 is applied to the end effector 414 of the robotic arm 40, sensors in joints 511 and 513 can each sense a torque and a force, respectively, and a sensor in joint 512 can sense a force. Figure 7B When the load 610 and load 620 are applied simultaneously to the connecting arm 413 of the robotic arm 50, the sensors in joints 511 and 512 can each sense one degree of freedom torque and one degree of freedom force. Figure 7C When applied to the end effector 414 and connecting arm 413 of the robotic arm 60, sensors in joints 511 and 512 can each sense one degree of freedom torque and two degrees of freedom force, and sensors in joint 513 can sense one degree of freedom torque and one degree of freedom force. Therefore, in this embodiment, two loads 610 and 620 can be accurately identified because when a load 630 (e.g., ...) is applied... Figure 6C The sensing results of the multi-degree-of-freedom sensor (as shown) differ from those obtained when two loads 610 and 620 are applied. Therefore, by utilizing multi-degree-of-freedom force and / or torque sensors, the robot can still accurately estimate each load even when different loads are applied at different locations.

[0032] In some embodiments, two adjacent joints of the robot can be equipped with six-degree-of-freedom force and torque sensors. Two adjacent joints (e.g., Figure 1 Joints 125 and 126 in the diagram can be represented by joint N and joint (N+1), and the sensor readings on the corresponding joints can be... and (Converted to the same coordinates), they are all six-degree-of-freedom vectors. This is the total inertial force between the two joints. Assume a single-point contact is applied to the connecting arm between the two joints (e.g., ...). Figure 1 Any point on the connecting arm 136 in the process, then the six degrees of freedom information of the contact point (e.g., two degrees of freedom position on the connecting arm, one degree of freedom normal force, two degrees of freedom shear force, and one degree of freedom torsional force) can be based on... The calculation is performed, where T is the transformation function for solving the problem. This contact point information can be used for a variety of purposes, including better human-robot interfaces and safety.

[0033] For example, a robot can better understand point contacts on its body, enabling it to react more appropriately to protect the human operator and distinguish between abnormal collisions and normal interactive contact. In another example, a human operator can draw specific patterns with specific force distributions on specific connecting arms of the robot to give certain commands. Building on the previous analysis, this is achieved by projecting onto the corresponding joints. This allows for the calculation of the impact of point contact on adjacent joints, enabling the local torque controller of each joint to generate additional torque to compensate for this impact. Therefore, the entire arm can better resist disturbances on the arm without affecting the operational task and the end effector.

[0034] In the above embodiments, a six-degree-of-freedom force and torque sensor was utilized. In some embodiments of the invention, a sensor capable of measuring force and torque information with fewer degrees of freedom can be used to detect simpler contact forces on the arm. For example, when the user applies only a normal force to the arm without shear or torsional friction, a four-degree-of-freedom sensor that cannot measure forces and torsion along and around the axis of the connecting arm can be used to sense contact forces on the connecting arm.

[0035] refer to Figure 1 In some embodiments, each of the joints 121-127 of the robot 100 may be equipped with a multi-degree-of-freedom force and / or torque sensor, which in some respects may be a six-degree-of-freedom force and torque sensor. In this embodiment, additional redundant sensors in the arm may be fused together to improve sensing accuracy. For example, averaging sensor outputs from multiple joints of the stationary robotic arm in the same force direction can reduce the overall sensing error in that direction. If a sensor has noise or error standard deviation in a sensing direction... Then, when each joint has a seven-degree-of-freedom arm and a six-degree-of-freedom sensor, the standard deviation of the error can be transformed into Force and torque sensors in the joints can be used to accurately estimate the location, orientation, and magnitude of external contact forces on each of the robot's connecting arms 131-137, providing useful information for more advanced human-robot interactions and interfaces. Because the torque and force sensors do not need to be placed inside the joints 131-137, they can be more flexibly mounted anywhere on the corresponding joints to gain design benefits, such as simplifying wiring configuration or optimizing joint design for better dynamics and control performance.

[0036] It is understood that those skilled in the art can utilize the claimed invention to its fullest extent using the foregoing description without further elaboration. The examples and embodiments disclosed herein should be interpreted as illustrative only and do not limit the scope of the invention in any way. It will be apparent to those skilled in the art that variations can be made to the details of the above embodiments without departing from the basic principles discussed. In other words, various modifications and improvements to the embodiments specifically disclosed in the foregoing description are within the scope of the appended claims. For example, any suitable combination of features of the various described embodiments is contemplated.

Claims

1. A robotic arm, comprising: Multiple joints; Multiple connecting arms are sequentially connected by the multiple joints; Each of at least two of the joints includes a sensor configured to measure force and torque information of six degrees of freedom (DOF) applied to a corresponding joint in at least two of the joints, the sensor being a six-DOF force and torque sensor; The sensor is located between the input end of a corresponding joint among at least two of the joints and the preceding connecting arm among the plurality of connecting arms, or the sensor is located between the output end of a corresponding joint among at least two of the joints and the following connecting arm among the plurality of connecting arms; the sensor is located outside the input end and the output end of the joint.

2. The robotic arm according to claim 1, characterized in that, Each of the plurality of joints includes a sensor configured to measure force and torque information applied to more than one of the six degrees of freedom on a corresponding joint in the plurality of joints.

3. The robotic arm according to claim 1, characterized in that, At least two of the joints each further include a sensor circuit board that communicates with the sensor, and The sensor circuit board is located at the input end of one of the corresponding joints of at least two of the joints and is adjacent to the sensor.

4. The robotic arm according to claim 1, characterized in that, At least two of the joints also include additional sensors, and The sensor is located between the output end of a corresponding joint among at least two of the joints and the next connecting arm among the plurality of connecting arms, and the additional sensor is located between the input end of a corresponding joint among at least two of the joints and the previous connecting arm among the plurality of connecting arms.

5. The robotic arm according to claim 4, characterized in that, The sensors and additional sensors of each of at least two of the joints are substantially the same.

6. The robotic arm according to claim 1, characterized in that, The sensor is used to estimate the location, orientation, and magnitude of the external contact force on each of the multiple connecting arms based on force and torque information.

7. The robotic arm according to claim 1, characterized in that, The bearing is positioned between the input and output ends of the joint to allow relative rotation between the input and output ends.

8. The robotic arm according to claim 1, characterized in that, The structural stiffness of the sensor in the actuation direction of one of the at least two joints is lower than the structural stiffness of the sensor in other directions.

9. The robotic arm according to claim 8, characterized in that, The sensor is configured to measure the torque applied in the actuation direction to a corresponding joint of at least two of the joints, and to measure force and torque information of at least one of the other five degrees of freedom applied to a corresponding joint of at least two of the joints.

10. A robot comprising a robotic arm as described in any one of claims 1 to 9; the robot comprising a plurality of joints and a plurality of connecting arms sequentially connected via the plurality of joints. in, Each of at least two of the joints includes a sensor configured to measure force and torque information applied to a corresponding joint in one of the at least two joints in six degrees of freedom (DOF), the sensor being a six-DOF force and torque sensor; The sensor is located between the input end of a corresponding joint among at least two of the joints and the preceding connecting arm among the plurality of connecting arms, or the sensor is located between the output end of a corresponding joint among at least two of the joints and the following connecting arm among the plurality of connecting arms; the sensor is located outside the input end and the output end of the joint.

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